Pump



July 31, 1962 Filed July 9, 1959 Fial R. J. PSCHUNDER PUMP 2 Sheets-Sheet l BY @ww INVENTOR Ralph J'Pschunder Jim ATTORNEYS July 31, 1962 R. J. PSCHUNDER PUMP 2 Sheets-Sheet 2 Filed July 9, 1959 Fit-3.3

m 9 5 M Q A15 4 5 9 3 7 INVENTOR Ralph J. P5 chunder ATTORNEYS United States Patent Bfidfifih? Patented July 31, 1962 Filed July 9, 1959, Ser. No. 826,057 3 Clm ms. ll. 103-173) This invention relates to reciprocating piston pumps, and more particularly to those piston pumps in which the discharge flow from the working chambers is controlled by a spring-biased check valve.

The check valves usually employed in Less pumps are of the poppet type, i.e., the valves have movable heads which carry flat annular valving surfaces that abut similar surfaces formed on the cylinder block and encircling the discharge passages leading from the working chambers. A valve of this type is shown in Huber Patent 2,381,056, granted August 7, 1945. While this kind of valve is satisfactory in pumps which operate at speeds below about 5,000 r.p.m., they possess two characteristics which limit their usefulness in high speed pumps, i.e., those operating at about 35,000 rpm. In the first place, every time the valve head seats, both the head and the cylinder block are subject to an impact load. These impacts occur once each revolution so it will be apparent that in a high speed pump the life expectancy of the poppet valve is short. The other limiting characteristic relates to the fact that the area of the valve head subject to the pressure in the working chamber is less than the area subject to the discharge pressure of the pump. As a result, the pressure in the working chamber must buildup to a value considerably greater (for example 800 psi.) than the discharge pressure before the check valve opens. These pressure pulsations and the noise they produce are intolerable in a pump operating at speeds as high as 35,000 r.p.m.

The object of this invention is to provide an improved discharge check valve for reciprocating piston pumps which is free from the disadvantage mentioned above and therefore is particularly useful in high speed pumps. According to the invention, the check valve is of the sliding plunger type, that is, the valve 'head is fitted with a control edge which cooperates with a fixed valve land to control flow from the pump working chamber to the discharge port. Attached to the valve head is an hydraulic stop mechanism which limits motion of the valve head in the closing direction. This mechanism utilizes the compressibility of a liquid as a cushion and, since liquids are much more compressible than solid metals, this arrangement reduces materially the wear produced by the impact loads imposed on the cylinder block. Furthermore, in this type of valve, the areas subject to the pressures in the working chamber and the discharge port can be balanced easily and therefore pressure pulsations and noise can be reduced.

The preferred embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which:

FIG. 1 is an axial sectional view of a constant displacement opposed piston pump employing the improved check valve; the check valve 38 being shown in the closed position with its stem 43 just interrupting flow from bore 4-2, and the check valve 38' being shown in the open position.

FIG. 2 is a sectional view taken on line 2--Z of FIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 1 showing the check valves.

FIG. 4 is an enlarged perspective view of one of the stem guides.

Referring to FlG, l, the pump comprises a housing 11 I housing and the annular discharge manifold 15. A cylinder block 16, containing two circular series of aligned cylinder bores 17 and 17', is pressed into a bore formed in housing 11 and isolates the manifold 15 from the space 14. Pump pistons 13 and 18 reciprocate in the bores 17 and 17', respectively, and define, with the inner closed ends of these bores, variable volume working chambers 19 and 19'. Extending between each pair of aligned cylinder bores 17 and 17' is a coaxial plunger bore in which is mounted a piston plunger 21. These plungers 21 abut the inner ends of pump pistons 18 and 18. Piston shoes 22 and 22 are mounted for universal movement on the outer ends of the pistons 18 and 18, respectively.

Extending through, but spaced radially from, an axial bore formed in cylinder block 16, is a drive shaft 23 containing an axial bore 24 and radial passages 25 and 25' which are aligned with the inlet passages 26 and 26', respectively, formed in cylinder block 16. The shaft 23 is journalled in bearings 27 and 27 located on opposite sides of cylinder block 16 and is provided with a conventional running seal 28 at its left end. Carried by the drive shaft 23 are two swash plates 29 and 29'; the former being an integral part of the shaft and the latter being spline-d to it, as shown. The cam faces 31 and 31' of these swash plates lie in parallel planes and are in sliding engagement with the piston shoes 22. The piston plungers 21 are of such length that the shoes carried by the two sets of pump pistons are maintained in operative engagement with the swash plates 29 and 29'.

Coaxial with the two series of cylinder bores 17 and 17' are two similar series of bores 32 and 32; there being the same number of bores in these series as in the series 17 and 17'. Each bore in the series 32 contains two ports 33 and 34 which are separated by a fixed valve land 35 and which are connected with one of the working chambers 19 and with the discharge manifold 15 by passages 36 and 37, respectively. Similar ports 33' and 34', valve land 35' and passages 36 and 37 are provided for each bore 32'. Reciprocable in bores 32 and 32' are the check valves 38 and 38', respectively, having control edges 39 and 39' which cooperate with the fixed lands 35 and 35 to control communication between ports 33 and 34 and between ports 33 and 34', respectively. A valve stem guide 41, containing axial bores 42 and 42' for receiving the stems 43 and 43' of check valves 38 and 33, is mounted at the junction of each pair of aligned bores 32 and 32 ad is held in place by a pin 44. The opposite ends of each stem guide 4-1 are provided with cross slots 45 and 45' which, when the check valves are open, establish communication between the axial bores 42 and 42 and the ports 33 and 33, respectively. The outer ends of the bores 32 and 32' are closed and sealed by threaded plugs 46 and 46, and the spaces 47 and 47' between these plugs and the check valves 38 and 38 are connected with the discharge manifold 15 by passages 48 and 48' so that discharge pressure urges the check valves in the closing direction. The check valves 38 and 3-8 are also urged closed by light coil springs 49 and 49, respectively.

During operation, fluid entering inlet port 12 passes through space 14- into the axial bore 24 formed in shaft 23 and is expelled, by centrifugal pumping action, through the radial passage 25 into the inlet passages 26. When each pump piston 13 moves outward on its suction stroke, it uncovers the associated inlet passage 26 and permits fluid to flow into the working chamber 19. On the inward or discharge stroke, the passage 26 is closed and the fluid is forced from working chamber 19 through passage 36. The fluid displaced by each piston 18 is conveyed to the associated bore 32 through port 33 where and develops a force tending to shift this valve in the opening direction. The pressure in bore 32 is transmitted to the axial bore 42 through the slot 45 and the radial clearance between stem 43 and the bore 42 so that an displaced by the associated piston .18 passes to the discharge port 13 through port 34, passage 37 and manifold 15. a a 7 As each piston 18 reaches its top dead center position and commences to move on itssuction stroke, the pressure in passage 36 and bore 32 drops and the spring 4?,

together with the pressure fluid in'space 47,"shifts the check valve 38in the closing direction. This movement causes stem 43 to displace fluid from bore 42 through slot 45 and as it proceeds, the restriction to fiow from that bore becomes progressively greater. As aresult, the pressure in bore 42 builds-up and develops a retarding force on face 52. After edge 39 has overtravelled land 35, and thus interrupted communication between ports 33 and 34, the right end of stem 43 closes completely communication between bores 42 and 32 through slot 45. This action traps fluid in bore 42 and forms an hydraulic stop for check valve 38.

The check va1ves38 operate in the same manner as the check valves 38 so further description of operation is deemed unnecessary.

As stated previously, the drawings and description relate only to a preferred embodiment of the invention,

Since many changes can be made in the structure of this embodiment without departing from the inventive concept,the following claims should provide the sole meas ure of the scope of the invention.

What is claimed is: I V 1. In a reciprocating piston pump having a working 'it acts upon the annular face 51 of the check valve 38 4 4 a chamber and a discharge port, the improvement which comprises a valve bore containing two longitudinally spaced ports separated by a fixed'valve land; a first passage connecting one of the ports with the working chamher and a second passage connecting the other. port with the discharge port; a sliding plunger type valve member reciprocable in the bore and having'a control edge ar. ranged to move between a flow-establishing position outside the fixed valve. land and a flow-interrupting position inside the fixed valve land for controlling flow between th'e two ports; first and second reaction surfaces carried by the valve member and subject to the pressures'in the first and second passages, respectively, the first surface developing a force which urges the valve member toward the flow-establishing position and the second surface developing a force which urges the valve member in the opposite direction; a spring urging the valve member in the flow-interrupting direction; and an hydraulic stop for a limiting movement of the valve member in the. flow-interrupting direction, the stop being effective aiter the valve member has reached said flow-interrupting position.

2 The improvement defined in claim 1 in which the hydraulic stop comprises a cylinder bore having one closed end; a piston reciprocable in the cylinder bore and connected with the valve member; and a third'pasa sage connecting the cylinder bore with the first passage, the parts being so arranged that the third passage is closed by the piston after the valve member has reached the. flow-interrupting position.

3. The improvement defined in claim 2 in which the efiective area of the second reaction surface equals the sum of the efiective' areas of the first reaction surface and the piston.

References Cited in the file of this patent UNITED STATES PATENTS 558,034 Brown et a1. Apru14, 1896 1,539,617 Williston May 26, 1925 1,631,142 Masters June 7, 1927 2,318,963 Parker May 1171, 1943 2,361,881 Sheppard Oct. 31, 1944 2,806,430 Osborne Sept. 17, 1957 

